The Precision Micrometer Screw Gauge
This micrometer is composed of a frame, anvil, thimble, and ratchet stop. Used in most mechanical trades for precision measurement. Micrometers use the principle of a screw to amplify small distances that are too small to measure. The accuracy of a micrometer derives from the accuracy of the thread form.
Government Printing Office The Official Gazette of the United States Patent Office (Washington, DC: Government Printing Office, 1895)
Courtesy the private collection of Roy Winkelman